Method and system for performing audio ducking for headsets

ABSTRACT

A method performed by an audio source device. The method receives a first audio signal and a second, different audio signal and encodes the first audio signal and the second audio signal, wherein the first audio signal is encoded differently than the second audio signal. The method generates a first data packet that comprises the first encoded audio signal and a first volume level and a second data packet that comprises the second encoded audio signal and a second volume level, wherein the first volume level is lower than the second volume level and transmits, over a wireless connection, the first and second data packets as a dual audio stream to an audio output device.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of and priority to U.S. ProvisionalPatent Application Ser. No. 63/083,773, filed Sep. 25, 2020, which ishereby incorporated by this reference in its entirety.

FIELD

An aspect of the disclosure relates to an audio source device thattransmits several audio signals and metadata as a dual audio stream toan audio output device that ducks and mixes the audio signals togetherfor output according to the metadata. Other aspects are also described.

BACKGROUND

Headphones are an audio device that includes a pair of speakers, each ofwhich is placed on top of a user's ear when the headphones are worn onor around the user's head. Similar to headphones, earphones (or in-earheadphones) are two separate audio devices, each having a speaker thatis inserted into the user's ear. Both headphones and earphones arenormally wired to a separate playback device, such as an MP3 player,that drives each of the speakers of the devices with an audio signal inorder to produce sound (e.g., music). Headphones and earphones provide aconvenient method by which the user can individually listen to audiocontent without having to broadcast the audio content to others who arenearby.

SUMMARY

An aspect of the disclosure is a method performed by an audio sourcedevice (e.g., a multimedia device, such as a smartphone). The audiosource device receives a first audio signal (e.g., playback audio, suchas music) and a second, different audio signal (e.g., notificationaudio, such as a virtual personal assistant (VPA) response). The sourcedevice encodes the first audio signal and the second audio signal, wherethe first audio signal is encoded differently than the second audiosignal. For instance, both audio signals may be encoded by compressingeach of the audio signals at different compression bit rates, where thefirst audio signal is compressed at a lower compression bit rate than acompression bit rate the second audio signal. The audio source devicegenerates a first data packet that includes the first encoded audiosignal (e.g., as one or more playback audio frames) and a first volumelevel and a second data packet that includes the second encoded audiosignal (e.g., as one or more notification audio frames) and a secondvolume level, where the first volume level is lower than the secondvolume level. For instance, both data packets may store their respectivevolume levels as metadata in headers. The audio source device transmits,over a wireless connection (e.g., BLUETOOTH connection), the first andsecond data packets as a dual audio stream to an audio output device(e.g., a wireless headset) that is configured to process the first andsecond encoded audio signals contained therein according to theirrespective volume levels to produce a mixed audio signal for outputthrough a speaker.

In another aspect, the audio source device may dynamically adjust thecompression of one or more of the audio signals (e.g., in real-time).For example, the audio source device may adjust the compression bitrate(s) based on the bandwidth or available throughput of the wireless(e.g., BLUETOOTH) connection with the audio output device. This wirelessconnection may fluctuate based on various conditions (e.g., based on thenumber of devices that are in wireless communication with the audiosource device, based on environmental conditions, etc.). As the wirelessconnection changes, the audio source device may determine differentcompression rates in order to account for those changes. For example,the audio source device may determine that there is a reduction inavailable bandwidth for transmitting the dual audio stream over thewireless connection and adjust at least one of the first and secondcompression bit rates based on the reduction. As a result, the audiosource device may change the compression bit rate of the first audiosignal and/or of the second audio signal while streaming both signals tothe audio output device.

According to another aspect of the disclosure, a method is performed bythe audio output device. Specifically, the output device receives, overa wireless connection, the dual audio stream that is transmitted by theaudio source device, and decodes the first and second encoded audiosignals, respectively. Once decoded, the audio output device may storeboth decoded audio signals into different buffers. The audio outputdevice may apply a first scalar gain associated with the first volumelevel received within the dual audio stream to the first decoded audiosignal and may apply a second scalar gain associated with the secondvolume level received within the dual audio stream to the second decodedaudio signal to generate first and second gain-adjusted audio signals,respectively. The audio output device drives the speaker with a mix ofthe first and second gain-adjusted audio signals.

In one aspect, the volume levels contained within the dual audio streammay be based on a user volume setting of the audio output device.Specifically, the user volume setting may be determined based on userinput at the audio output device. For example, the audio output devicemay include an input device (e.g., a volume knob), which when adjustedby the user defines the user volume setting. The audio output devicetransmits, over the wireless connection, the user volume setting, wherethe first volume level may be less than the user volume setting and thesecond volume level is 1) greater than the first volume level and 2)less than or equal to the user volume setting.

The above summary does not include an exhaustive list of all aspects ofthe disclosure. It is contemplated that the disclosure includes allsystems and methods that can be practiced from all suitable combinationsof the various aspects summarized above, as well as those disclosed inthe Detailed Description below and particularly pointed out in theclaims. Such combinations may have particular advantages notspecifically recited in the above summary.

BRIEF DESCRIPTION OF THE DRAWINGS

The aspects are illustrated by way of example and not by way oflimitation in the figures of the accompanying drawings in which likereferences indicate similar elements. It should be noted that referencesto “an” or “one” aspect of this disclosure are not necessarily to thesame aspect, and they mean at least one. Also, in the interest ofconciseness and reducing the total number of figures, a given figure maybe used to illustrate the features of more than one aspect, and not allelements in the figure may be required for a given aspect.

FIG. 1 shows an audio system that includes an audio source device and anaudio output device.

FIG. 2 shows a block diagram of the audio source device that isconfigured to transmit a dual audio stream that includes playback audioand notification audio according to one aspect.

FIG. 3 shows a block diagram of an audio output device that isconfigured to receive the dual audio stream and output the playbackaudio and notification audio according to another aspect.

FIG. 4 is a flowchart of one aspect of a process to transmit the dualaudio stream.

FIG. 5 is a flowchart of one aspect of a process to receive the dualaudio stream and output the audio contained therein.

DETAILED DESCRIPTION

Several aspects of the disclosure with reference to the appendeddrawings are now explained. Whenever the shapes, relative positions andother aspects of the parts described in a given aspect are notexplicitly defined, the scope of the disclosure here is not limited onlyto the parts shown, which are meant merely for the purpose ofillustration. Also, while numerous details are set forth, it isunderstood that some aspects may be practiced without these details. Inother instances, well-known circuits, structures, and techniques havenot been shown in detail so as not to obscure the understanding of thisdescription. Furthermore, unless the meaning is clearly to the contrary,all ranges set forth herein are deemed to be inclusive of each range'sendpoints.

Wireless communication capabilities are available in a broad array ofaccessory devices that can be configured to communication with an audiosource device, such as a multimedia device (e.g., smart phone). Forinstance, wireless audio output devices, such as a wireless headset or apair of wireless earphones, can connect via a wireless personal areanetwork (WPAN) connection to the source device in order to receive anaudio stream. In one aspect, the WPAN connection may be a BLUETOOTHconnection using any BLUETOOTH communication protocol. To stream ahigh-quality playback audio signal (e.g., music), the audio sourcedevice packetizes the playback audio (e.g., partitions the data intounits (or frames) for transmission) according to the protocol (e.g.,Advanced Audio Distribution Profile (A2DP)), and transmits the packetsover an over-the-air (or wireless) radio frequency (RF) signal to thewireless audio output device. The received packets are stored in a longbuffer in the output device in order to provide continuous audioplayback in situations when future packets are dropped (e.g., due totransmission interference). The playback audio data in the buffer arede-packetized and processed for audio output through one or morespeakers. This process is repeated while audio output is desired at theaudio output device.

When outputting the playback audio, it may be desirable to outputdifferent audio content. In particular, while streaming music, the audiosource device may transmit notification audio (e.g., a virtual personalassistant (VPA) response) to the audio output device for playback. Thismay be performed in one of several methods. For example, the audiosource device may cease transmitting the playback audio signal and inits place stream the notification audio as a notification audio signalto the audio output device for output. As a result, however, thelistener of the audio output device may experience an abrupt pause ofthe music while the notification is played back. This abrupt pause maybe undesirable. Instead, as another method the audio source device maystream a mix of the playback audio signal and the notification audiosignal. In this case, the audio source device may first adjust eachaudio signal's gain differently, such that the playback audio has alower volume than the notification audio, The audio source device thenmixes both signals together to produce a mixed audio signal that maythen be transmitted to the output device, which when played backtransitions the playback audio to a lower volume while the notificationaudio is outputted at a higher volume than the current playback audio.This method, however, has drawbacks. For example, if the user were tochange the volume setting (e.g., reduce the volume) while thenotification is being played back, there would be significant latencybetween the time the volume is changed and when the user experiences thechange in volume. In this case, once the volume setting is changed,although the audio source device may adapt the gain adjustment to theaudio signals based on the changed volume setting, the audio outputdevice will have to exhaust the long buffer of the mix that was producedand transmitted by the audio source device from before the volumesetting was changed. As a result, the user may experience a significantundesirable latency, such as 200 milliseconds or higher before thechange is experienced.

The present disclosure solves this problem by providing an audio systemin which two individual audio streams are transmitted as a dual audiostream by the audio source device to the audio output device, ratherthan as a mixed audio signal. Specifically, the audio source devicewirelessly transmits the dual audio stream that contains 1) at least one(first) data packet that contains the playback audio signal and 2) atleast one (second) data packet that contains the notification audiosignal. Each of the data packets may also include volume levelsassociated with each respective audio signal. In particular, the firstdata packet may include a first volume level for the playback audiosignal and the second data packet may include a second volume level forthe notification audio signal. The audio source device may transmit thedual audio stream to the audio output device, which is configured toprocess the audio streams contained therein according to theirrespective volume levels to produce a mixed audio signal for output.Thus, rather than the audio source device performing audio signalprocessing operations, such as ducking (e.g., applying scalar gainsassociated with their respective volume levels) to each individual audiosignal, the audio output device may perform these operations, therebyreducing (or eliminating) latency due to the output device's buffer.

Conventional methods may be unable to wirelessly transmit multipleindividual audio streams due to limited bandwidth of wirelessconnections, such as a BLUETOOTH connection between two devices. Forexample, some codecs, such as Advanced Audio Coding (AAC) may streamaudio (e.g., stereo sound) at a bit rate between 256-345 Kbps (e.g.,based on the sample rate). The present disclosure solves this problem byencoding (or compressing) each of the individual audio streamsdifferently in order to satisfy the connection's bit rate. For instance,the audio source device may compress the playback audio signal more thanthe notification audio signal, such that the playback audio signal has alower compression bit rate than a compression bit rate of thenotification audio signal. By compressing the playback audio signalmore, the audio source device is able to transmit both individualstreams while not exceeding the limited bandwidth between the twodevices.

FIG. 1 shows an audio system 1 that includes an audio source device 2and an audio output device 3. In one aspect, the audio system mayinclude other devices, such as a remote electronic server (not shown)that may be communicatively coupled to either the audio source device,the audio output device, or both, and may be configured to perform oneor more operations as described herein. As illustrated, the audio outputdevice is a headset that is arranged to direct sound into the ears ofthe wearer. Specifically, the headset is an earphone (or in-earheadphone or earbud) that is positioned on (or in) the user's right ear.In one aspect, the headset may include a pair of earphones, a leftearphone for the user's left ear and a right earphone for the user'sright ear. In this case, each earphone may be configured to output atleast one audio channel of a playback (or program) audio (e.g., theright earphone outputting a right audio channel and the left earphoneoutputting a left audio channel of a two-channel input of a stereophonicrecording, such as a musical work). In some aspects, the earphone may bea sealing type that has a flexible ear tip that serves to acousticallyseal off the entrance of the user's ear canal from an ambientenvironment by blocking or occluding in the ear canal. In anotheraspect, the headset may be over-the-ear headphones that at leastpartially covers the user's ears. In some aspects, the headset may beon-ear headphones. In another aspect, the output device may be anyelectronic device that includes at least one speaker and is arranged tobe worn by the user and arranged to output sound by driving the speakerwith an audio signal.

In one aspect, the audio output device 3 may be any electronic devicethat is arranged to output sound into the ambient environment. Asdescribed herein, the device may be worn by (e.g., on a head of) theuser. Other examples may include the output device being part of atleast one of a stand-alone speaker, a smart speaker, a home theatersystem, or an infotainment system that is integrated within a vehicle.In another aspect, the audio output device may be any portable device,such as a tablet computer, a laptop computer, or a smartphone.

In one aspect, the audio source device 2 is a multimedia device, morespecifically a smart phone. In another aspect, the audio source devicemay be any electronic device that can perform audio signal processingoperations and/or networking operations. An example of such a device mayinclude a tablet computer, a laptop, a desktop computer, a smartspeaker, etc. In one aspect, the source device may be a portable device,such as a smart phone, as previously described. In another aspect, thesource device may be a head-mounted device, such as smart glasses, or awearable device, such as a smart watch.

As shown, the audio source device 2 is communicatively coupled to theaudio output device, via a wireless connection 4. For instance, thesource device may be configured to establish the wireless connectionwith the audio output device 3 via a wireless communication protocol(e.g., BLUETOOTH protocol or any other wireless communication protocol).During the established wireless (e.g., BLUETOOTH) connection, the audiosource device may exchange (e.g., transmit and receive) data packets(e.g., Internet Protocol (IP) packets) with the audio output device,which may include audio digital data. For example, the audio outputdevice may be paired with the audio source device such that the outputdevice receives one or more audio streams for output through one or morespeakers of the audio output device. More about streaming audio data byexchanging data packets is described herein.

In another aspect, the audio source device 2 may communicatively couplewith the audio output device via other methods. For example, bothdevices may couple via a wired connection. In this case, one end of thewired connection may be (e.g., fixedly) connected to the audio outputdevice, while another end may have a connector, such as a media jack ora universal serial bus (USB) connector, which plugs into a socket of theaudio source device. Once connected, the audio source device may beconfigured to drive one or more speakers of the audio output device withone or more audio signals, via the wired connection.

In some aspects, the audio source device 2 may be a part (or integratedwith) the audio output device 3. For example, as described herein, atleast some of the components of the audio source device (such as one ormore processors) may be a part of the audio output device. In this case,each of the devices may be communicatively coupled via traces that are apart of one or more printed circuit boards (PCBs) within the audiooutput device.

Turning now to FIG. 2, this figure shows a block diagram of the audiosource device that is configured to generate and transmit (e.g., via thewireless connection 4 shown in FIG. 1) a dual audio stream that includesplayback audio and notification audio according to one aspect. In oneaspect, the operations described in this figure may be in response tothe audio system I outputting an audible notification alert), via theaudio output device 3 while the output device is streaming playbackaudio. For instance, while the audio source device 2 is streaming musicto the output device, the source device may also transmit anotification, such as a VPA response in response to sensing a spokentrigger phrase by a listener. As an example, when sensing a triggerphrase of “Hey Hal, do you read me?” that is spoken by a user of theaudio source device, the notification may be “How can I help you Dave.”As a result of transmitting both the notification and the music, theaudio source device and the audio output device may perform one or moreoperations as describe herein. More about transmitting notifications andthe VPA is described herein.

The source device 2 includes a controller 90 may be a special-purposeprocessor such as an application-specific integrated circuit (ASIC), ageneral purpose microprocessor, a field-programmable gate array (FPGA),a digital signal controller, or a set of hardware logic structures(e.g., filters, arithmetic logic units, and dedicated state machines).The controller is configured to generate and transmit a dual audiostream, as described herein. More about the operations performed by thecontroller is described herein. In one aspect, operations performed bythe controller may be implemented in software as instructions stored inmemory of the audio source device (and/or memory of the controller) andexecuted by the controller and/or may be implemented by hardware logicstructures. In one aspect, the source device may include more elements,such as memory elements, one or more microphones, one or more speakers,and/or one or more display screens.

As illustrated, the controller 90 may have one or more operationalblocks, which may include a playback audio encoder 12, a notificationaudio encoder 13, a packetizer 14, and a volume control 15.

The controller 90 is configured to receive playback audio 20, as aplayback audio signal that may contain program audio, such as music, apodcast, or a movie soundtrack. For example, (e.g., a processor or thecontroller 90 of) the audio source device may be running a media playersoftware application that is retrieving and providing the playback audioto the controller. For instance, the playback audio may be retrievedfrom local memory (e.g., of the audio source device 2) and/or fromanother electronic device. In this case, the playback audio signal maybe streamed from a local device (e.g., communicatively coupled via wireor a local area network) or a remote electronic device (e.g., via theInternet), such as a remote server. In one aspect, the playback audiosignal may be a single (mono) audio channel. In another aspect, theplayback audio may be a two-channel input, namely left and rightchannels of a stereophonic recording of a musical work, or there may bemore than two audio channels, such as for example the entire audiosoundtrack in 5.1-surround format of a motion picture film or movie. Inone aspect, the playback audio may be digital audio (e.g., in the formof one or more audio frames), or analog audio.

In one aspect, the playback audio signal may include other audiocontent. For example, the signal may include a downlink signal that isobtained by the audio system 1 during a telephone call with anotherelectronic device.

The controller 90 may also be configured to receive notification audio21, as one or more notification (audio) signals that contain an audiblenotification. For example, (e.g., a processor or the controller 90 of)the audio source device may be running a software application that isconfigured to retrieve and provide notification audio, such as acalendar application, an alarm application, a navigation application,and/or a VPA application. For example, the alarm application maydetermine that an alarm notification is to be outputted at a particulartime (e.g., the alarm notification indicating that “It is 10 o'clock”).At that time, the application may retrieve the notification audio 21 andprovide the audio to the controller 90. In another aspect, thenotification audio 21 may be provided (or retrieved by the controller90) in response to user input. For example, the VPA application may beconfigured to monitor one or more microphone signals captured by one ormore microphones (which are not shown, but may be a part of the audiosource device 2, the audio output device 3, and/or a separate electronicdevice) that are arranged to convert sensed speech into microphonesignals. The VPA application may be configured to analyze the signals inorder to identify (e.g., recognize) the speech contained therein. In oneaspect, the speech may be a trigger phrase, question, and/or command. Inresponse, to the identified speech the VPA application may retrieve asuitable vocal response as the notification audio. For example, when theidentified speech that is spoken by a user of the audio source device isa question, such as “What time is it?”, the notification audio retrievedby the VPA application (e.g., from local memory or a remote source, suchas a remote server) may include a response to the question, such as “Itis 10 o'clock.”

In one aspect, the playback audio signal 20 and/or notification audiosignal 21 may be digital audio (e.g., Pulse-Code Modulation (PCM) audio,etc.). In another embodiment, the signals may be analog or optical audiosignals, in which case the controller may include a codec that isconfigured to convert these signals into digital form.

The playback audio encoder 12 and the notification audio encoder 13 areconfigured to encode the playback audio signal 20 and notification audiosignal 21, respectively. Although illustrated as being two separateencoders, they may be composed of a single encoder (e.g., programmedprocessor). The playback audio encoder 12 is configured to receive atleast a portion (e.g., one or more audio frames) of the playback audiosignal 20 (e.g., from local memory), and is configured to encode theplayback audio signal to produce an encoded playback audio signal 22.Specifically, the encoder 12 may encode each frame of the playback audiosignal 20 into an encoded playback audio frame. In one aspect, theencoder 12 may encode the playback audio signal using any suitable audiocodec, such as, e,g., Advanced Audio Coding (AAC), MPEG Audio Layer II,MPEG Audio Layer III, or Free Lossless Audio Codec (FLAC). Thenotification audio encoder 13 is configured to receive at least aportion (e.g., one or more audio frames) of the notification audiosignal 21, and is configured to encode the notification audio signal toproduce an encoded notification audio signal 23, In one aspect, bothencoders 12 and 13 may encode their respective audio signals accordingto the same audio codec (e.g., AAC). In another aspect, each of theencoders may use a different audio codec (e.g., the playback audioencoder 12 using MPEG Audio Layer II, while the notification audioencoder 13 uses AAC).

In one aspect, each of the encoders 12 and 13 may encode (or compress)their respective audio signals differently. Specifically, the playbackaudio encoder 12 may compress the playback audio signal 20 more than thenotification audio encoder 13 compresses the notification audio signal21. Thus, the encoded playback audio signal 22 may have a lowercompression bit rate than a compression bit rate of the encodednotification audio signal 23. In one aspect, the encoders may compresstheir respective audio signals before encoding them according to aparticular (or predefined) codec, such as AAC.

In one aspect, the encoders may determine the compression bit rate ofboth signals based predefined (or threshold) bit rates (e.g., as definedin a data structure that is stored in local memory). For instance, theplayback encoder may encode at a first predefined bit rate, while thenotification encoder may encode at a second different predefined bitrate. In another aspect, the encoders may determine the compression bitrate for their respective signals based on the wireless connectionbetween the two devices. As one example, both encoders may compress bothsignals based on a predetermined bit rate associated with the wirelessconnection. For example, a BLUETOOTH connection (of which both arecommunicatively coupled) may have a threshold bit rate of approximately345 Kbps (e.g., based on the sampling rate). In this case, the playbackencoder 12 and the notification encoder 13 may compress their respectiveaudio signals such that the combination has a bit rate that is less thanor equal to the threshold bit rate of the connection. In addition, theplayback encoder may compress the playback audio at a lower compressionrate than the notification rate, while maintaining the combined bit ratebelow the threshold. In one aspect, the playback audio 20 may becompressed with a lower bit rate than to the notification audio toprovide the notification with a higher sound quality than the playbackaudio, which will have a lower volume level during playback at the audiooutput device, as described herein. As yet another example, thecompression bit rates may be based on the codec that both encoders useto compress their respective audio signals for BLUETOOTH transmission,such that a combination of the bit rates of the compressed audio signalsis not greater than a threshold bit rate associated with the codec.

In one aspect, one or both of the encoders 12 and 13 may dynamicallyadjust its associated compression rate. For example, either of theencoders may adjust its rate of compression based on the bandwidth oravailable throughput of the wireless (e.g., BLUETOOTH) connection. Inone aspect, “bandwidth” may correspond to an amount of data that can besent from the audio source device to the audio receiver device in acertain period of time. In another aspect, as described herein,bandwidth or available throughput may correspond to a data bit rate (orthroughput) that is necessary for the source device 2 to transmit audiodata to the output device in order for the receiver device to render andoutput the audio data. During data transfer, however, this bandwidth oravailable throughput may change. For example, the bandwidth may varydepending on how many other devices are wirelessly communicating withthe audio source device and/or the audio output device. As anotherexample, throughput may change based on various environmental factors(e.g., network interference, etc.). in one aspect, the (e.g., encodersof the) audio source device may be configured to determine the (current)bandwidth or throughput of the wireless connection for transmitting datato the audio output device. In some aspects, the device may use any(known or unknown) method to make this determination. For example, theaudio source device may determine the throughput based on a round-triptime after transmitting one or more data packets. Based on thedetermined bandwidth, each of the encoders 12 and 13 may determine itsrespective compression bit rate. In another aspect, the encoders mayadjust their respective bit rates based on changes to the audio sourcedevice's throughput. For example, the controller 90 (or either of theencoders) may determine that there is a reduction in available bandwidthor throughput for transmitting (e.g., audio data, such as a dual audiostream, as described herein) over the wireless connection. Thisreduction may be based on any of the examples described herein upondetermining that there is a reduction, at least one of the encoders mayadjust its respective compression bit rate. Conversely, however, if thethroughput increases the encoders may increase their respectivecompression rates. Thus, in response to determining changes in thewireless connection, the encoders may adjust the compression rates.

In another aspect, the playback audio signal 20 and/or the notificationaudio signal 21 are encoded by their respective encoders at 100% volumelevel. Specifically, the encoded signals 22 and 23 are at a same volumelevel as their original signals 20 and 21, respectively. Thus, thecontroller 90 encodes the signals 20 and 21 without applying scalargains to increase or attenuate the signals. In another aspect, thecontroller may not perform any other audio signal processing operations(e.g., applying audio filters to spectrally shape the signals, etc.). Insome aspects, each of the encoded audio signals 22 and/or 23 may be atthe 100% volume level, regardless of the size (e.g., word length) ofeach of the signal's audio frames. In another aspect, encoding at 100%volume level may include encoding the signals at 0 dBFS, whichrepresents the highest loudness level of the signals before clippingoccurs.

The volume control 15 is configured to receive a user volume setting 25from the audio output device 3 (e.g., over the wireless connection 4).Specifically, the volume control 15 may receive the user volume setting(e.g., a percentage value, a gain value, etc. from the audio outputdevice 10 via the wireless connection 4. In one aspect, the volumecontrol 15 may receive the user volume setting when a volume input(e.g., input 49 shown in FIG. 3) of the audio output device is changedby a user (e.g., based on user input at the audio output device). Inanother aspect, the volume setting may be received periodically (e.g.,every ten seconds) from the audio output device (e.g., without userintervention). In another aspect, the volume control may receive theuser volume setting based on user input at the audio source device 2. Inthis case, the user of the audio source device 2 (and of the audiooutput device 3) may adjust the user volume setting at the audio sourcedevice based on user input (e.g., adjusting a physical control, such asa knob, etc.).

The volume control 15 is configured to determine different volume levelsfor the playback audio and the notification audio. In particular, thevolume control may determine a playback (first) volume level 28 for theplayback audio and a notification (second) volume level 30 for thenotification audio based on the received user volume setting. In oneaspect, the playback volume level is determined to be less than thenotification volume level. In another aspect, the notification volumelevel may be greater than the playback volume level and less than orequal to the user volume setting. in one aspect, the playback volumelevel and the notification volume level determined by the volume control15 are to be applied to the playback audio and notification audio,respectively by the audio output device, as described herein. In oneaspect, the volume levels are to be applied to (at least portions of)the playback and notification audio that are to be played back (e.g.,mixed together and outputted) contemporaneously. In one aspect, thevolume control may determine relative volume levels of both the playbackaudio and the notification audio based on the user volume setting 25 ofthe audio output device (and/or the audio source device). In one aspect,the volume control may define the notification volume level asequivalent to (or equal to) the user volume setting, while the firstvolume level is a reduction of the user volume setting. For example,when the user volume setting is indicated to be 60%, the notificationvolume setting may be defined as 60%, while the playback volume levelmay be defined at 5%. In another aspect, both volume levels may bedefined based on a percentage of the user volume setting. For instance,the notification volume level may be 90% of the user volume setting,while the playback volume level may be 10% of the user volume setting.in yet another aspect, both volume levels may be predefined volumelevels.

The packetizer 14 is configured to receive the encoded playback audiosignal 22 and the encoded notification audio signal 23, and isconfigured to receive the playback volume level 28 and the notificationvolume level 30. In one aspect, the volume levels received by thepacketizer are to be applied to the audio signals received from encoders12 and 13. The packetizer 14 is also configured to generate one or moreplayback (first) data packets each of which including at least a portionof the encoded playback audio signal (e.g., one or more encoded audioframes) as playback data and the (e.g., current) playback volume level28 (which may be stored as metadata in the packet's header). Inaddition, the packetizer 14 is configured to generate one or morenotification (second) data packets each of which including at least aportion of the encoded notification audio (e.g., one or more encodedaudio frames) as notification data and the (e.g., current) notificationvolume level 30 (which may be stored as metadata in the packet'sheader). In one aspect, each of the packet's headers may also includeadditional metadata, such as a synchronization number, timestamp, thevolume of the data stored therein, the codec type used by encoders 12and 13, etc.

The audio source device 2 is configured to transmit, over the wirelessconnection 4, the data packets generated by the packetizer 14 as a dualaudio stream 24 to the audio output device 3. Specifically, a wirelesstransceiver (e.g., radio frequency (RF) transceiver of the BLUETOOTHhardware lower stack) of the audio source device 2 (not shown) mayreceive the generated data packets from the packetizer 14 and wirelesslytransmit the data packets as the dual audio stream. In one aspect, thetwo types of data packets may be interweaved within the dual audiostream, such as a notification packet is positioned between two playbackpackets, as shown in this figure. As shown, the first packet (on the farright) is a playback data packet that includes playback data and anassociated volume level, followed by a notification data packet thatincludes notification data and an associated volume level. This patternis then repeated, thereby creating the dual audio stream 24. In anotheraspect, the data packets may be transmitted in groups (or chunks). Inanother aspect, the data packets may be transmitted in any order and/orconfiguration. As described herein, the playback audio and thenotification audio contained within the dual audio stream aretransmitted to the audio output device 3 for synchronized output.

FIG. 3 shows a block diagram of an audio output device 3 that isconfigured. to receive the dual audio stream 24 and output the playbackaudio and notification audio according to another aspect. This figureshows that the audio output device includes a controller 91, one or morespeakers 48, and a volume input (device) 49. In one aspect, the audiooutput device may include more or less elements, such as including oneor more microphones.

In one aspect, the controller 91 is configured to receive the dual audiostream 24, perform one or more audio signal processing operations uponone or both of the audio signals contained within the stream, and outputthe audio signals (e.g., as a mix). As shown, the controller 91 may haveone or more operational blocks, which may include an audio manager 40, aplayback decoder 41, a notification decoder 42, a playback buffer 43, anotification buffer 44, a (e.g., playback) gain stage 45, a (e.g.,notification) gain stage 46, and a mixer 47.

The audio manager 40 is configured to receive the dual audio stream 24from the audio source device 2 (e.g., via a wireless transceiver of theoutput device, not shown). The audio manager 40 is configured to extractthe audio data and metadata from the stream. Specifically, the managerextracts the encoded playback audio signal 22 (e.g., as one or moreencoded playback audio frames) and the encoded notification audio signal23 (e.g., as one or more encoded notification audio frames), containedwithin the dual audio stream 24. The audio manager is also configured toextract metadata from each data packet's header. For example, the audiomanager extracts a playback volume level 28 from each playback audiopacket and a notification volume level 30 from each notification audiopacket. More about the volume levels is describe herein.

The playback decoder 41 and the notification decoder 42 are configuredto decode the encoded playback audio signal 22 and the encodednotification audio signal 23, respectively, which were encoded using anysuitable audio codec, as described herein. Although illustrated as beingseparate blocks, operations of both decoders may be performed by a.single decoder that is configured to decode one or more audio signals.The playback decoder 41 is configured to receive the encoded playbackaudio signal 22 from the audio manager 40 and is configured to decodethe signal, producing a decoded playback audio signal. Similarly, thenotification decoder 42 is configured to receive the encodednotification audio signal 23 from the audio manager 40 and is configuredto decode the signal, producing a decoded notification audio signal. Inone aspect, each of the decoded audio signals and/or may maintain thesame compression bit rate, as the encoded audio signals 22 and 23,respectively. Thus, the decoded playback audio signal may have a lowercompression bit rate as a compression bit rate of the decodednotification audio signal, as described herein. The playback buffer 43is configured to receive and store the decoded playback audio signal,and the notification buffer 44 is configured to receive and store thedecoded notification audio signal. Specifically, each of the buffers maystore audio frames of each buffer's respective audio signal.

As described herein, the audio output device 3 is configured to duck atleast one of the playback audio and the notification audio for outputthrough one or more speakers 48. Specifically, the (playback) gain 45 isconfigured to receive or extract (e.g., one or more audio frames of)buffered playback audio signal from the playback buffer 43 and isconfigured to adjust a signal level of (e.g., by applying a first scalargain value to) the buffered signal to produce a (first) gain-adjustedaudio signal. Similarly, the (notification) gain 46 is configured toreceive or extract (e.g., one or more audio frames of) bufferednotification audio signal from the notification buffer 44 and isconfigured to adjust a signal level of (e.g., by applying a secondscalar gain value to) the buffered signal to produce a (second)gain-adjusted audio signal. In one aspect, each of the gains areconfigured to receive audio frames of respective audio signals forsynchronized output (or playback) by the audio output device.

In one aspect, each of the gains 45 and 46 are configured to adjusttheir associated scalar gain values based on volume levels that arecontained within the dual audio stream 24. In particular, the gain 45 isconfigured to receive a playback volume level 28 that is extracted fromthe dual audio stream 24 by the audio manager, and is configured to set(or define) the associated first scalar gain value based on the playbackvolume level. Similarly, the gain 46 is configured to receive anotification volume level 30 that is extracted from the dual audiostream 24 by the audio manger 40, and is configured to set (or define)the associated second scalar gain value based on the notification volumelevel. In one aspect, the scalar gain value is proportional to thevolume level. Thus, as a volume level increases, the scalar gain valuemay increase.

In one aspect, both gains 45 and 46 may be based on respective volumelevels that are contained within the dual audio stream 24. For example,gain 45 may be defined by a playback volume level 28 that is extractedfrom a most-recently received playback packet, and gain 46 may bedefined by a notification volume level 30 that is extracted from amost-recently received notification placket by the audio manager 40. Asa result, the gain of audio frames extracted from buffers 43 and 44 maybe adjusted by gains 45 and 46, respectively, according to amost-recently extracted volume level. Thus, the gains may be adjusted inreal-time based on changes in volume levels within the dual audio stream24. This is in contrast with conventional methods in which volumechanges are experienced by the user of the audio output device onlyafter the long buffer is depleted, as described herein. As a result, thepresent disclosure reduces (or eliminates) this latency.

In another aspect, the scalar gain values of the gains 45 and/or 46 maybe based on a current portion of a respective audio signal that is beinggain-adjusted by the gains. For example, the gain 45 may be defined by avolume level 28 that is associated with a portion of the playback audiosignal that is retrieved from the playback buffer 43 and is being gainadjusted by the gain 45. For example, the volume level may have beenassociated with the portion of the playback audio signal received withinthe dual audio stream 24 (e.g., within one or more playback datapackets).

The mixer 47 is configured to receive the gain-adjusted audio signalsfrom the gains 45 and/or 46, and is configured to mix both signals toproduce a mixed (output) audio signal. In one aspect, the mixer mayperform matrix mixing operations that mixes and/or routes the audiosignals to one or more outputs, such as speaker 48. In one aspect, themixer 47 may perform digital and/or analog mixing operations.

In another aspect, the mixer 47 may spatially render the received audiosignals, such that one or more sounds contained within are experiencedby the user as different sound sources. For example, the mixer 47 mayapply spatial (e.g., head-related transfer functions (HRTFs)) that arepersonalized for the user of the output device 3 in order to account forthe user's anthropometrics. In this case, the mixer 47 may producebinaural audio signals, a left signal for the left speaker (e.g., of aleft earphone of the headset 3) and a right signal for the right speaker(e.g., speaker 48), which when outputted through respective speakersproduces a 3D sound (e.g., gives the user the perception that sounds arebeing emitted from a particular location within an acoustic space). Inone aspect, when there are multiple sounds, the mixer may apply spatialfilters separately to each (or a portion of the sounds) and then mix thespatially filtered sounds into a set of mixed signals.

Although each of the computational blocks are illustrated as beingcontained within (e.g., being performed by) the controller 91, one ormore may be separate electronic devices. For example, at least one ofthe buffers 43 and 44 may be separate memory devices, which iscommunicatively coupled with the controller 91. As another example, themixer 57 may be a separate audio processor.

The volume input 49 is configured to determine (define or set) the uservolume setting 25 at the audio output device 3. In one aspect, thevolume input may determine the user volume setting based on user inputat the audio output device. For example, the volume input 49 may be aninput device, such as a physical volume control (e.g., knob) that isconfigured to set the volume setting in response to receiving input froma user (e.g., twisting the volume knob). For instance, the volumesetting may be based on an amount of rotational movement of the volumeknob. In another aspect, the volume input may be one or more userinterface (UI) controllers that may be displayed on a display screen(e.g., of the audio source device and/or of the audio output device). Asshown, the audio output device 3 transmits (e.g., over a wirelessconnection, which may be the same connection through which the dualaudio stream is received) the user volume setting 25 (defined by thevolume input 49) to the audio source device. In one aspect, the audiooutput device may transmit the setting in response to the volume inputreceiving user input to adjust the user volume setting. As anotherexample, the output device may transmit the setting periodically.

FIGS. 4 and 5 are flowcharts of processes 70 and 80, respectively, forperforming audio ducking for headsets. In one aspect, the processes areperformed by the audio system 1. For instance, process 70 may beperformed by the (e.g., controller 90 of the) audio source device 2,while process 80 may be performed by the (e.g., controller 91 of the)audio output device 3. Thus, these figures will be described withreference to FIGS. 1-3.

Regarding FIG. 4, this figure is a flowchart of one aspect of theprocess 70 to transmit the dual audio stream 24. The process 70 beginsby the controller 90 receiving a first audio signal (e.g., playbackaudio 20) and a second, different audio signal (e.g., notification audio21) (at block 71). The controller 90 receives a user volume setting(e.g., volume level) at the audio output device 3 (at block 72). Forexample, the controller 90 may receive the volume setting from the audiooutput device (e.g., over the wireless connection 4). The controller 90determines a first volume level for the first audio signal and a secondvolume level for the second audio signal based on the user volumesetting (at block 73). As described herein, the volume control 15 isconfigured to determine the volume levels of the playback audio signaland the notification audio signal based on the user volume setting (orlevel) at the audio output device.

The controller 90 encodes the first audio signal (e.g., as a firstencoded audio signal) and encodes the second audio signal (e.g., as asecond encoded audio signal) (at block 74). Specifically, the signalsmay be encoded by compressing the signals according to differentcompression bit rates. For example, the playback audio encoder 12 maycompress (e.g., each audio frame associated with) the first audio signalat a first compression bit rate and the notification audio encoder 13may compress (e.g., each audio frame associated with) the second audiosignal at a second, different compression bit rate, where the firstcompression bit rate is lower than the second compression bit rate. Thecontroller 90 generates one or more first (e.g., playback) data packetsthat include (e.g., different portions of) the first encoded audiosignal and the first volume level, and generates one or more second(e.g., notification) data packets that include (e.g., different portionsof) the second encoded audio signal and the second volume level, whereboth volume levels are metadata stored in headers of their respectivedata packets (at block 75). In one aspect, each of the (e.g., playbackand/or notification) data packets include one or more audio frames ofthe respective audio signal. The controller 90 transmits, over awireless connection (e.g., connection 4 of FIG. 1), the data packets asa dual audio stream 24 to the audio output device 3 (at block 76). Inone aspect, the audio output device is configured to process the encodedfirst and second audio signals contained within the dual audio streamaccording to their respective volume levels to produce a mixed audiosignal for output through one or more speakers. More about theoperations of the audio output device is described herein.

In one aspect, the controller 90 of the audio source device 2 mayperform at least some of the operations of process 70 for each ofseveral portions (e.g., audio frames) of both first and second audiosignals. As a result, the controller 90 may dynamically adapt data to betransmitted within the dual audio stream based on changes within theaudio system. For example, for a first obtained portion of both audiosignals (e.g., a first audio frame of the first audio signal and a firstaudio frame of the second audio signal), the controller 90 may determinerespective volume levels based on a received user volume setting fromthe audio output device 3. For a second subsequently received portion ofeither of the first and second audio signals, however, the received uservolume setting may be different than the previously received user volumesetting (e.g., based on user input by the user at the audio outputdevice to reduce the volume). As a result, the controller of the audiosource device may determine different volume levels for the secondsubsequently obtained portion based on this change. Similarly, thecontroller of the audio source device may dynamically adapt the encodingof the audio signals based on changes within the audio system, asdescribed herein.

FIG. 5 is a flowchart of one aspect of the process 80 to receive thedual audio stream 24 and output the audio (e.g., via speaker 48)contained therein. The process 80 begins by the controller 91 of theaudio output device 3 receiving, over a wireless connection (e.g., aBLUETOOTH connection, such as the connection 4 illustrated in FIG. 1),one or more first data packets and one or more second data packets asthe dual audio stream 24 from the audio source device, the first datapacket(s) including a first encoded audio signal and a first volumelevel and the second data packet(s) including a second encoded audiosignal and a. second volume level, where the first volume level is lowerthan the second volume level and the first encoded audio signal isencoded differently than (e.g., having a lower compression bit rate thana compression bit rate of) the second. encoded audio signal (at block81).

The controller 91 decodes the first and second encoded audio signals,producing a first decoded audio signal and a second decoded audiosignal, respectively (at block 82). The controller 91 stores the decodedaudio signals in first and second buffers (e.g., playback buffer 43 andnotification buffer 44 of FIG. 3), respectively (at block 83). Thecontroller 91 applies a first scalar gain associated with the firstvolume level to the first decoded audio signal and applies a secondscalar gain associated with the second volume level to the seconddecoded audio signal to generate first and second gain-adjusted audiosignals, respectively (at block 84). For example, the controller 91 mayretrieve (e.g., one or more audio frames of) the decoded playback audiosignal stored within the playback buffer 43 and may retrieve (e.g., oneor more audio frames of) the decoded notification audio signal storedwithin the notification buffer 44. In one aspect, the controller 91 mayretrieve audio frames that are for synchronized playback by the audiooutput device (e.g., portions of audio signals that are to be mixedtogether and played back at the same time). As described herein, thevolume levels may be associated with data packets that have beenmost-recently received within the dual audio stream. Thus, in oneaspect, the volume levels may be different than volume levels that werecontained within the same data packets as the retrieved audio frames(e.g., in a previously received portion of the dual audio stream 24). Inanother aspect, however, the volume levels may be the same (or similar)to the volume levels contained within the same data packets that hadcontained the retrieved audio frames when received within the dual audiostream. The controller 91 generates a mixed audio signal (or mix) of thefirst and second gain-adjusted audio signals (at block 85). Thecontroller 91 drives at least one speaker (e.g., speaker 48) of theaudio output device 3 with the mix (at block 86).

Some aspects may perform variations to the processes 70 and 80 describedherein. For example, the specific operations of at least some of theprocesses may not be performed in the exact order shown and described.The specific operations may not be performed in one continuous series ofoperations and different specific operations may be performed indifferent aspects.

In one aspect, at least some of the operations of processes 70 and 80may be performed by the audio system 1 in response to receiving userinput. For example, and as described herein, a notification application(e.g., a VPA application) executing within the (e.g., audio sourcedevice 2 of the) audio system may receive user input, such as a voicecommand, question, and/or trigger phrase. In response, the audio sourcedevice may obtain (or retrieve) the second audio signal (e.g., from thenotification audio source 11), which may contain an audible response tothe user input. In another aspect, the processes may automatically beperformed by the notification application (e.g., based upon adetermination that an audible notification needs to be outputted by theaudio output device). For example, a calendar application may determinethat an audible reminder (e.g., an alarm sound) needs to be outputted ata particular time of day.

In another aspect, these processes may be performed while the audiosystem 1 is outputting the first audio signal, which may be a playbackaudio signal (e.g., containing music). In that case, the audio sourcedevice may obtain the first audio signal and stream the signal to theaudio output device for playback. In response to determining that anaudible notification needs to be outputted, the audio source device mayobtain the second audio signal, which may be a notification audio signalat block 71 and proceed with the remaining operations to transmit a dualaudio stream to the audio output device. As a result, once the secondaudio signal is (e.g., entirely) transmitted to the audio output device,the audio source device may continue streaming the first audio signal tothe audio output device.

Personal information that is to be used should follow practices andprivacy policies that are normally recognized as meeting (and/orexceeding) governmental and/or industry requirements to maintain privacyof users. For instance, any information should be managed so as toreduce risks of unauthorized or unintentional access or use, and theusers should be informed clearly of the nature of any authorized use.

As previously explained, an aspect of the disclosure may be anon-transitory machine-readable medium (such as microelectronic memory)having stored thereon instructions, which program one or more dataprocessing components (generically referred to here as a “processor”) toperform the network operations and audio signal processing operations,as described herein. In other aspects, some of these operations might beperformed by specific hardware components that contain hardwired logic.Those operations might alternatively be performed by any combination ofprogrammed data processing components and fixed hardwired circuitcomponents.

While certain aspects have been described and shown in the accompanyingdrawings, it is to be understood that such aspects are merelyillustrative of and not restrictive on the broad disclosure, and thatthe disclosure is not limited to the specific constructions andarrangements shown and described, since various other modifications mayoccur to those of ordinary skill in the art. The description is thus tobe regarded as illustrative instead of limiting.

In some aspects, this disclosure may include the language, for example,“at least one of [element A] and [element B].” This language may referto one or more of the elements. For example, “at least one of A and B”may refer to “A,” “B,” or “A and B.” Specifically, “at least one of Aand B” may refer to “at least one of A and at least one of B,” or “atleast of either A or B.” In some aspects, this disclosure may includethe language, for example, “[element A], [element B], and/or [elementC].” This language may refer to either of the elements or anycombination thereof. For instance, “A, B, and/or C” may refer to “A,”“B,” “C,” “A and B,” “A and C,” “B and C,” or “A, B, and C.”

What is claimed is:
 1. A method performed by an audio source device, themethod comprising: receiving a first audio signal and a second,different audio signal; encoding the first audio signal and the secondaudio signal, wherein the first audio signal is encoded differently thanthe second audio signal; generating a first data packet that comprisesthe first encoded audio signal and a first volume level and a seconddata packet that comprises the second encoded audio signal and a secondvolume level, wherein the first volume level is lower than the secondvolume level; and transmitting, over a wireless connection, the firstand second data packets as a dual audio stream to an audio outputdevice.
 2. The method of claim 1, wherein encoding the first audiosignal and the second audio signal comprises compressing the first audiosignal according to a first compression bit rate and compressing thesecond audio signal according to a second compression bit rate, whereinthe first compression bit rate is lower than the second compression bitrate.
 3. The method of claim 2, further comprising determining thatthere is a reduction in available bandwidth for transmitting the dualaudio stream over the wireless connection; and adjusting at least atleast one of the first and second compression bit rates based on thereduction.
 4. The method of claim 1 further comprises receiving, overthe wireless connection, a user volume setting of the audio outputdevice; and determining the first and second volume levels based on theuser volume setting.
 5. The method of claim 1, wherein the first audiosignal comprises playback audio and the second audio signal comprisesnotification audio, both of which are for synchronized output by theaudio output device.
 6. The method of claim 5, wherein the notificationaudio comprises a virtual personal assistant (VPA) response.
 7. Themethod of claim 1, wherein the audio output device is a wirelessheadset.
 8. The method of claim 1, wherein the wireless connection is aBLUETOOTH connection.
 9. An audio output device, comprising: aprocessor; and memory having instructions stored therein which whenexecuted by the processor causes the audio output device to receive,over a wireless connection, a first data packet and a second data packetas a dual audio stream, the first data packet comprising a first encodedaudio signal and a first volume level and the second data packetcomprising a second encoded audio signal and a second volume level,wherein the first volume level is lower than the second volume level andthe first encoded audio signal is encoded differently than the secondencoded audio signal; decode the first and second encoded audio signals;apply a first scalar gain associated with the first volume level to thefirst decoded audio signal and apply a second scalar gain associatedwith the second volume level to the second decoded audio signal togenerate first and second gain-adjusted audio signals, respectively; anddrive a speaker of the audio output device with a mix of the first andsecond gain-adjusted audio signals.
 10. The audio output device of claim9 further comprising a first audio buffer for storing the first decodedaudio signal; and a second audio buffer for storing the second decodedaudio signal, wherein the instructions to apply the first and secondscalar gains comprises extracting the first and second decoded audiosignals from the first and second audio buffers, respectively.
 11. Theaudio output device of claim 9, where the memory has stored thereinfurther instructions to determine a user volume setting based on userinput at the audio output device; and transmit, over the wirelessconnection, the user volume setting, wherein the first volume level andthe second volume level are based on the user volume setting.
 12. Theaudio output device of claim 11, wherein the first volume level is lessthan the user volume setting and the second volume level is 1) greaterthan the first volume level and 2) less than or equal to the user volumesetting.
 13. The audio output device of claim 9, wherein the audiooutput device is a wireless headset.
 14. The audio output device ofclaim 9, wherein the first encoded audio signal is encoded differentlyby having a lower bit rate than a bit rate of the second encoded audiosignal.
 15. The audio output device of claim 9, wherein the first audiosignal comprises playback audio and the second audio signal comprises avirtual personal assistant (VPA) response.
 16. An audio source device,comprising: a processor; and memory having instructions stored thereinwhich when executed by the processor causes the audio source device toreceive a first audio signal and a second, different audio signal,encode the first audio signal and the second audio signal, wherein thefirst audio signal is encoded differently than the second audio signal,generate a first data packet that includes the first encoded audiosignal and a first volume level and generate a second data packet thatincludes the second encoded audio signal and a second volume level, thefirst volume level being lower than the second volume level, andtransmit, over a wireless connection, the first and second data packetsas a dual audio stream to an audio output device.
 17. The audio sourcedevice of claim 16, wherein the instructions to encode the first andsecond audio signals comprises instructions to compress the first audiosignal according to a first compression bit rate and compress the secondaudio signal according to a second compression bit rate, wherein thefirst compression bit rate is lower than the second compression bitrate.
 18. The audio source device of claim 17, wherein the memory hasfurther instructions to determine that there is a reduction in availablebandwidth for transmitting the dual audio stream over the wirelessconnection; and adjust at least one of the first and second compressionbit rates based on the reduction.
 19. The audio source device of claim16, wherein the memory has further instructions to receive, over thewireless connection, a user volume setting of the audio output device;and determine the first and second volume levels based on the uservolume setting.
 20. The audio source device 16, wherein the first audiosignal is playback audio and the second audio signal is notificationaudio, both of which are for synchronized output by the audio outputdevice.
 21. The audio source device of claim 20, wherein thenotification audio comprises a virtual personal assistant (VPA)response.
 22. The audio source device of claim 16, wherein the audiooutput device is a wireless headset.
 23. The audio source device ofclaim 16, wherein the wireless connection is a BLUETOOTH connection.